Adjustable pole extensions for use in electromagnetic hardness testers



Sept. 8, 1964 R. c. SCOTT 3,147,614

ADJUSTABLE POLE EXTENSIONS FOR UsE IN ELECTROMAGNETIC HARDNESS TESTERSFiled June 16. 1960 R D T H. m T N u mw H l .l V s m N W E m m M LHHD mE 4 E F O m b m R K 5 Y I B r n 2 l- I I M & m w 6 1 a 2?? 0 0 Oddi Q846.m M m 3R6 T E RE E f l C E w u m H\ flid w E O 2 ul 2lllllllllllllllllllll IIL I 2 H ATTORNEYS United States Patent Q3,147,614 ADJUSTABLE POLE EXTENSIONS FOR USE IN ELECTROMAGNETIC HARDNESSTESTERS Robert C. Scott, 340 Common St., Belmont, Mass.

Filed June 16, 1960, Ser. No. 36,667

2 Claims. (Cl. 73- 81) This invention relates to adjustable poleextensions for use in electromagnetic hardness testers of the kind shownand described in US. Patent No. 2,693,698, issued No- Vem'ber 9, 1954 toRobert C. Scott. That patent describes a hardness tester which isadapted for testing ferromagnetic work pieces having variously formedsurfaces, that can be affixed and firmly held by electromagnetic meansto the work during the making of hardness tests, and that demagnetizesthe work after completion of a test to facilitate removal of the testerfrom engagement with the work. The electromagnetic means comprises acylindrical electromagnet having an annular recess to form inner andouter concentric pole cores which contact the work, a coil placed withinthe recess, and an armature comprising the work piece itself. Thisarrangement affords a high magnetic force to retain the tester securelyin place on the work piece against the mechanical forces exerted duringthe testing operation.

For conducting hardness tests on a work piece having a surface which iscurved or non-planar, my aforementioned patent discloses a shoe adapter,forming an extension of the electromagnet poles, which may be secured tothe lower surface of the electromagnet to reduce the cumulative air gapbetween the electromagnet and the curved work surface, thus increasingthe lifting or withholding force to a value adequate to resist themaximum opposing force exerted by a penetrator in making a hardness testupon the work surface. The work-contacting surface of the shoe adapterdescribed forms an arcuate portion of a cylinder having an inherentlyfixed radius. As

a consequence, it is desirable to provide a variety of shoe. adapters ofdiffering surface radii of curvature, for con-,

ducting tests upon curved work surfaces of differing diameter orirregular form.

The primary object of this invention is to provide improved means forminimizing the air gap between the pole piece of an electromagnetichardness tester and work pieces having curved or otherwise non-planarsurfaces.

It is a further object of this invention to provide improved adjustablepole extension means for use with electromagnetic hardness testers, toaccommodate ferromagnetic work pieces having various forms and a widerange of radii of curvature with a minimum cumulative air gap betweenthe hardness tester and the work piece.

An important feature of the inventionresides in the provision ofauxiliary adjustable pole pieces capable of adjustment not only as tolength but also as to the angular posture of the faces which bear uponthe work piece. In consequence the work engaging structure of thehardness tester may elfectively be modified to conform to the surfacecontour of a work piece and thereby minimize the air gap.

It is a feature of this invention that the improved pole extension meansutilizes. arelativelysmall number of pole extension plates capable ofbeing assembled in a variety of gr'oupsto afford a wide range ofeffective radii of curvature and are effective to minimize thecumulative air gap between an electromagnet and work surfaces of widelyvarying form.

It is a further object of this invention to provide improved adjustablepole extension means for use with electromagnetic hardness testers,applicable either directly to an electromagnetic structure having planarsurfaces, or by means of an improved shoe adapter to a cylindricalelectromagnetic structure.

3,147,614 Patented Sept. 8, 1964 Further objects and advantages of myinvention will become apparent as the following description proceeds,referring to the accompanying drawing, in which:

FIG. 1 is a view in side elevation of a preferred embodiment of myimproved pole extension means, including a shoe adapter for mounting thepole extension plates upon an electromagnetic hardness tester;

FIG. 2 is a top plan view of the pole extension means of FIG. 1;

FIG. 3 is a view in side elevation of a set of pole extension plateswhich are used in various groups to form a portion of the pole extensionmeans;

FIG. 4 is a view in front elevation of one of of FIG. 3; and

FIG. 5 is a view in side elevation of a fragmentary portion of anelectromagnetic hardness tester of modified form, shown in combinationwith the pole extension plates.

Referring to FIG. 1, a fragmentary portion 10 of an electromagnetichardness tester is shown in broken lines, comprising cylindricalelectromagnetic means for holding a Work piece during a testingprocedure, as more fully shown and described in my aforementioned US.Patent No. 2,693,698. The electromagnet is designed to provide a liftingor tractive force between the face of the magnet and the surface of awork piece whose hardness is to be measured of sufiicient magnitudeadequately to resist the maximum opposing force of a penetrator (notshown) which is caused to indent the work surface for determination ofits hardness. The work piece, which is ferromagnetic acts as thearmature of the magnetic circuit. It is necessary that the magnetictractive forcebe sufficiently great to prevent any movement Whateverbetween the face of the magnet and the surface of the work.

The present invention is directed toward the problem of minimizing thecumulative air gap between the face of the electromagnetic hardnesstester 10 and work pieces whose surfaces have a variety of forms ofradii of curvature. An illustrative work piece of cylindrical form isshown in broken lines in operative relation to the hardness tester. Thework piece forms only a tangential line contact with the surface of theelectromagnet, and it is there fore desirable to provide pole extensionmeans, especially for the outer pole, to reduce the cumulative air gapbetween these members, so as to prevent excessive reduction in themagnetic force retaining the Work piece in testing position.

In carrying out my invention in part, I provide at least two sets ofpole extension means comprising plates 11, 12 and 13, which are morefully shown in FIGS. 3 and 4. The plates are trapezoidal incross-section, being respectively formed with opposite side edge planesurfaces the plates 11a and 11b, 12a and 12b, and 13a and 13b, each ofwhich forms a different angle with the parallel major surfaces of thecorresponding plate. The number of plates in the set and the range inside edge surface angles are not critical to the invention, but I preferto'provide three plates in each set as shown, having angles ranging fromapproximately 65 to degrees, at 5 degree intervals. For convenience inselection, I prefer to stamp an identifying mark (not shown) on theplates adjacent to each side edge. Each plate is also formed with a pairof mounting slots 14 extending transversely to its side edges, of whichone pair in plate 11 is best shown in FIG. 4. T

Referring again to FIGS. 1 and 2, I provide a shoe adapter 16, having acircular opening 17, for adjustably mounting groups of plates 11, 12 and13 upon the lower outer surface of the cylindrical hardness tester 10.The shoe adapter and its component parts, and also plates 11, 12 and 13,are made of soft iron or low content carbon steel slowly annealed aftermachining, in order to provide a magnetic circuit having maximum fluxdensity and therefore maximum tractive force. On opposite sides thereof,adapter 16 is slotted at 18 and split at 19, to allow for flexing andclamping of the frame. The adapter is secured to the outer pole coresurface of the electromagnet structure by a clamping screw 20, receivedin suitably bored and threaded holes 21 and 22. For supporting theplates, the adapter is formed with plane edge surfaces 23 and 24, whichintersect the major surfaces of the shoe frame in parallel lines andconverge downwardly toward the work piece. Pre-selected groups of twoplates from each set, shown as plates 11 and 12 by way of illustration,are secured to opposite sides of the adapter upon surfaces 23 and 24 bywashers 25 and cap screws 26, the screws extending through slots 14 andbeing threaded into the adapter.

The selection and adjustment of the pole extension plates is made withreference to the diameter or form of of the work piece, to conform tothe condition that each of :side edge surfaces 11a and 12a, as well asthe lower surface of the hardness tester, contact the surface of thework piece tangentially. As used herein, the term tangentially is usedwith reference to a cross-section of the work piece, with which the sideedge surfaces form point contact; thus, tangential contact is abutmentalong each point of a line of contact between a side edge surface andthe work piece. Thus it will be apparent that in testing a cylindricalwork piece whose centerline falls substantially at the intersection ofthe planes of shoe frame surfaces 23 and 24, plates having side edgesurfaces approximately normal to their major surfaces, such as surface12b, should be selected. When testing larger or smaller work pieces, theside edge surface angles to be selected become more acute. The positionsof the plates relative to the shoe adapter 16 are also adjusted to meetthe aforementioned condition, and this adjustment is accommodated by.

relatively moving screws 26 along slots 14 until surfaces 11a and 12acontact the work piece.

The tangential abutment of the side edge surfaces of the pole extensionplates upon the work piece minimize the cumulative air gapbetween theelectromagnet and the Work piece, thus maintaining the value of thetractive force at a high level adequate to maintain the work piece inposition during a hardness test.

It will be apparent that by selecting pole extension plates having sideedge surfaces which form appropriate angles relative to their majorsurfaces, both irregular surfaces and round surfaces Whose radii fall ina range between infinity and a minimum whose value depends upon the formand size of the shoe adapter 16, may be hardness tested according to thedescribed mode of operation. An alternate form of pole extension platescomprising a larger number of relatively thin plates with their endfaces at right angles relative to their sides may also be used,especially on surfaces where the radius of curvature is relativelylarge; however, a smaller cumulative air gap is achieved by usingrelatively few plates, as previously described.

A second embodiment of my improved pole extension means for hardnesstesters is shown in FIG. 5, in which the shoe adapter is eliminated, andthe pole extension plates are mounted directly upon a hardness testerThis device differs from the hardness tester shown in FIG. 1, anddescribed by my aforementioned patent, only 'with respect to thephysical configuration and arrangement of the electromagnet structure,which comprises a rectangularly shaped, rather than cylindr'icallyshaped, flat-faced type electromagnet.

' FIG. 1.

In order that pole extension plates may be fastened directly to theouter pole cores of the rectangular electromagnet structure, thisstructure is formed with longitudinally-extending parallel flanges 38and 39 having plane edge surfaces 40 and 41, respectively. Thesesurfaces correspond in function to surfaces 23 and 24 in the shoeadapter of the embodiment shown in FIG. 1, and eliminate the need forsuch an adapter in the rectangular electromagnet structure. Groups ofplates 11 and 12' are secured directly to the surfaces 40 and 41 bymeans of washers and screws 26'. The construction and operation of thehardness tester and the pole extension means are otherwise identicalwith those of the embodiment of The embodiment of FIG. 5 provides theadditional advantage that for electromagnet structures of equal size,the minimum radius of curved surfaces that may be hardness tested isless than the minimum radius of curved surfaces that may be hardnesstested with the circular type of electromagnet structure.

Although I have shown and described specific embodiments of my inventionfor illustrative purposes, it is to be understood that the invention isnot limited to the specific mechanical and electrical details described.Various changes and modifications may occur to those skilled in the artwithout departing from the spirit and scope of the invention, and Itherefore intend in the appended claims to cover all such changes andmodifications.

What I claim as new and desire to secure by Letters 1 Patent is:

1. In a hardness tester the combination comprising electromagnetic meanshaving a planar face, for engaging a work piece, adjustable mountingmeans secured to said electromagnetic means and forming two planar sideI surfaces intersecting the plane of said face in parallel lines, andpole extension means comprising a plurality of ferromagnetic plates eachhaving substantially planar major surfaces and a planar side edgesurface, said plates being arranged in two stacked groups, each of saidgroups being adjustably secured to a corresponding one of the sidesurfaces of said mounting means, with said side edge surfaces extendingoutwardly from said face with a common component of direction to engagethe surface of a work piece, the plates of each group being slidablerelative to one anotherfor adjustment of the relative positions of theside edge surfaces to conform to the contours of a selected work piece,whereby the hardness tester may be engaged and disengaged with a seriesof similar Work pieces without re-adjusting the groups of plates, saidside edge surfaces forming various angles with the major surfaces ofsaid plates, the angle of each side edge surface being such as to formtangential contact of the plane of that surface with the surface of theselected work piece.

2. The combination recited in claim 1,in which said side surfaces ofsaid mounting means lie in intersecting planessu'ch that said two groupsof plates converge from said face of said electromagnetic means in thedirection of extension of said plates therefrom.

References Cited in the file of this patent UNITED STATES PATENTS

1. IN A HARDNESS TESTER THE COMBINATION COMPRISING ELECTROMAGNETIC MEANSHAVING A PLANAR FACE, FOR ENGAGING A WORK PIECE, ADJUSTABLE MOUNTINGMEANS SECURED TO SAID ELECTROMAGNETIC MEANS AND FORMING TWO PLANAR SIDESURFACES INTERSECTING THE PLANE OF SAID FACE IN PARALLEL LINES, AND POLEEXTENSION MEANS COMPRISING A PLURALITY OF FERROMAGNETIC PLATES EACHHAVING SUBSTANTIALLY PLANAR MAJOR SURFACES AND A PLANAR SIDE EDGESURFACE, SAID PLATES BEING ARRANGED IN TWO STACKED GROUPS, EACH OF SAIDGROUPS BEING ADJUSTABLY SECURED TO A CORRESPONDING ONE OF THE SIDESURFACES OF SAID MOUNTING MEANS, WITH SAID SIDE EDGE SURFACES EXTENDINGOUTWARDLY FROM SAID FACE WITH A COMMON COMPONENT OF DIRECTION TO ENGAGETHE SURFACE OF A WORK PIECE, THE PLATES OF EACH GROUP BEING SLIDABLERELATIVE TO ONE ANOTHER FOR ADJUSTMENT OF THE RELATIVE POSITIONS OF THESIDE EDGE SURFACES TO CONFORM TO THE CONTOURS OF A SELECTED WORK PIECE,WHEREBY THE HARDNESS TESTER MAY BE ENGAGED AND DISENGAGED WITH A SERIESOF SIMILAR WORK PIECES WITHOUT RE-ADJUSTING THE GROUPS OF PLATES, SAIDSIDE EDGE SURFACES FORMING VARIOUS ANGLES WITH THE MAJOR SURFACES OFSAID PLATES, THE ANGLE OF EACH SIDE EDGE SURFACE BEING SUCH AS TO FORMTANGENTIAL CONTACT OF THE PLANE OF THAT SURFACE WITH THE SURFACE OF THESELECTED WORK PIECE.